This invention relates to sampling of air contaminants and particularly to passive air samplers of the type worn as a badge.
Passive air samplers are devices worn by personnel working in environments in which it is desirable to monitor exposure to various contaminants in the air, usually organic vapors. Such devices are known as badges because they can be clipped or otherwise temporarily fastened to the user""s clothing and worn there for a predetermined period of time, usually the entire shift or other working period in the atmosphere in question. The badges are called passive samplers because there is no pump or other accessory to assure the flow of air through it. Sampling relies on simple exposure to the atmosphere, not a measured or predetermined flow volume, but sampling badges may be distinguished from indicating badges, in that indicating badges may change color in the presence of a specific contaminant. In a sampling badge, extraction of the contaminants such as volatile organics from the air is accomplished by adsorbents in the badge. They are usually granular, made of porous polymer or sometimes activated carbon, and may or may not be treated to enhance the ability to adsorb a particular organic chemical.
Where the identification and quantification of the adsorbed material is to be performed by gas chromatography, the used adsorbent is subjected to thermal desorption and/or flushed with an inert gas such as nitrogen for sending to the gas chromatograph. For use in the gas chromatograph, the inert gas containing the desorbed contaminant is passed through a standard thermal desorption sampler tube which contains a second adsorbent. The material is then analyzed by the standard gas chromatographic techniques, which involve passing a further inert gas through the thermal desorption sampler tube.
Patents illustrating passive air sampling badges include Nelms et al U.S. Pat. No. 4,040,805 and Esch et al U.S. Pat. No. 4,205,043. See also Obermayer U.S. Pat. No. 4,258,000, Braun et al U.S. Pat. No. 3,950,980, Vo-Dinh U.S. Pat. No. 4,680,165 and Underhill et al U.S. Pat. No. 6,050,150. None of these describes the features of the present invention.
In the conventional process of interest in the present review, the contaminant is first picked up on an adsorbent in the badge, the contaminant is desorbed from the badge adsorbent and picked up on the chromatograph adsorbent, and then desorbed again for the acutal analysis. This process has been criticized for having too many steps, which are time-consuming and may be a source of error, and for excessive adsorbing and desorbing, which can also lead to error. In addition, whether or not the adsorbent must be removed from the badge for the initial desorbing step, the badge must be manipulated or even taken apart to get at or remove the adsorbent in some way for the first desorbing step. A simpler device and method for passive sampling and analysis would advance the art.
We have invented a device and method for the passive sampling of air which involves only one desorption step. It is simple to use and less subject to error than systems used in the past.
Our passive sampler is designed to permit a simple transfer of the adsorbent from the badge directly into an empty thermal desorption sample tube for use in a gas chromatograph. Our invention includes a passive air sampler comprising particulate adsorbent and a container therefor, the container including an opening for draining to empty the particular adsorbent by gravity from the container and having a shape to facilitate the draining.